FIGS. 1 and 2 are diagrams illustrating a conventional radiation power measurement method wherein an electromagnetic signal is directly received from an antenna in an open area test site (OATS) or an anechoic chamber.
As shown, a maximum radiation power or an effective radiation power (ERP) is measured in a standard test site, e.g., an open area test sites (OATS) or an anechoic chamber. The conventional radiation power measurement method will be described.
An equipment under test (EUT) 101 is located on a turntable of the standard test site (step 1), a transmission antenna 102 is located to be opposite to a test antenna 103, and then a signal having the highest power is written by moving the test antenna up and down ranging a few meters, e.g., in case of ANSI std., 1 m˜6 m (step 2). By rotating the turntable 100 by a predetermined angle, e.g., ANSI std., 45°, seven additional values are written by repeating the step 2 (Step 3). Then, the transmitter under test 101 is replaced with a half-wave vertical antenna 112 (step 4). The half-wave vertical antenna 112 should be located so that the center of the antenna is identical to that of the EUT, and the antenna is connected to a radio frequency (RF) signal generator 111 having known output values. Path losses are written and an effective radiation power (ERP) is computed based on the path losses.
The conventional radiation power measurement method is based on an EelectroMagnetic Interference (EMI) measurement method, and measures/estimates the maximum radiation power or the ERP by receiving an electromagnetic signal on the antenna in the OATS or anechoic chamber.
However, the conventional radiation power measurement method performed in the OATS or the anechoic chamber have drawbacks that it takes much time to measure radiation from a test object because of direct measurement by antenna, a maintenance fee for the standard test site costs high, and there are a lot of measurement errors because of environmental uncertainty.
Also, in estimation of the ERP/a total radiation power (TRP), it is preferred that a radiation field is estimated on spherical surface in free space. However, the conventional measuring method uses a cylindrical scanning method, and therefore, there is a drawback that a receiving field can be devaluated.
FIG. 3 is a diagram showing a conventional radiation power measurement method in a semi-anechoic chamber, and FIG. 4 is a diagram showing a conventional radiation power measurement method in an anechoic chamber.
Referring to FIG. 3, the conventional radiation power measurement method in the semi-anechoic chamber has the same drawbacks as the conventional radiation power measurement method described above with reference to FIGS. 1 and 2. The conventional measuring method takes a long time to measure the power and a high maintenance fee. Also, since there is reflection due to the ground plane, a measurement error is large. The conventional measuring method uses a sphere scan, and the radiation field can be devaluated. In the conventional measuring method in the anechoic chamber described with reference to FIG. 4, the measurement error is small, however, it take a long time to measure the power and a high maintenance fee.